I don't have the names right now, but the best is to get yourself a studio that will play VST instruments (Free one available with every copy of Computer Music magazine) and there are a number of free Vocoders, as well as a couple of VSTs that just do "robot voice" (or similar) The name Delay Lama comes to mind, but it's not a voice changer, I think it's a voice simulator (free VST, or at least it was free when I got it...)
If you like that, you should definitely give 'Fantomas' album 'Directors Cut' a good listening to. I think you'd really like it. That and Mike Patton(of 'Mr. Bungle/Fantomas/Tomahawk/Peeping Tom/Faith No More') is a f'ing genius IMO. Amazon link to 'Directors Cut', as it's not currently on iTunes: http://tinyurl.com/y8ur988